An in-vehicle system to be installed in an automobile includes an ECU (Electro Control Unit) called a BCM (Body Control Module). An I/O device (I/O: Input/Output) is connected to the BCM with a dedicated signal line, and the BCM controls the I/O device.
For in-vehicle systems as described above, there is a problem, which is that the number of signal lines connected to the BCM increases with an increase of I/O devices to be controlled.
To solve this problem, Patent Literature 1 discloses a method in which signal lines of a plurality of I/O devices are accommodated in multiplex transmission units placed at various parts of a vehicle, and these multiplex transmission units are interconnected with multiplex transmission channels.
On the other hand, in-vehicle systems require safety for preventing a serious accident even if a system failure occurs, and ISO 26262 has been standardized internationally as a safety-related standard.